318 



BEGONIACE^E. 



[Diclinous Exogk.ns. 



Order CVII. BEGONIACE^E.— Begoniads. 



Begoniaceae, R. Brown in Congo, 464. (1818) ; Endl. Gen. cciii.; Meisner,p. 336. 

 Diagnosis. — Cucurbital Exogens with dry fruit and placenta -projecting and meeting in 



the axis. 



Herbaceous plants or succulent under-shrubs, with an acid juice. Leaves alternate, 

 toothed, rarely entire, oblique at the base. Stipules large, scarious. Flowers pink, in 



cymes. Flowers <J <j> . Calyx ad- 

 herent. Sepals coloured ; in the 

 $ 4, 2 within the others and smaller; 

 in the $ 5, imbricated, two smaller 

 than the rest, or 8, of which 4 are 

 petaloid. £ Stamens indefinite, 

 distinct, or combined into a solid 

 column ; anthers collected in a 

 head, 2-celled, continuous with the 

 filaments, clavate, the connective 

 very thick, the cells minute, bursting 

 longitudinally. <j? Ovary adherent, 

 winged, 3-celled, with 3 large 

 placentse meeting in the axis ; 

 ovules anatropal ; stigmas 3, 2- 

 lobed, sessile, somewhat spiral. Fruit 

 membranous, capsular, winged, 3- 

 celled, with an indefinite number of 

 minute seeds ; bursting by slits at the base on each side of the 

 wings. Seeds with a transparent thin testa marked by reticulations, 

 which are oblong at the sides and contracted at either extremity ; 

 embryo very cellular, without albumen, with a blunt round radicle 

 next the hilum. 



It is not a little curious that the opinions of Botanists concerning 

 the affinity of these well-known plants should remain so undecided up to the present day. 

 I formerly supposed the Order related to Hydrangea from some resemblances in its seeds, 

 &c. ; others have approximated it to Buckwheats on account of the stipules, 3-cornered 

 fruit, and coloured calyx. Link places it near Umbellifers ; Von Martius next Sceevo- 

 lacese ; Meisner with Spurgeworts ; and the tendency to the production of 4 in the 

 sepals and petals, as evinced by Eupetalum, has led to the opinion that it may be related 

 to the epigynous Myrtal Alliance, its seeds being indefinite and destitute of albumen. 

 And that some near relation does exist between such plants and Begonia, is rendered 

 more probable by Bertolonia maculata, which has the winged fruit and much the habit 

 of that genus. Nevertheless, these are but distant points of approach ; and the real 

 affinities seem to be with, Cucurbits, with which Begoniads accord in the unisexual 

 flowers, peculiar stigmas, and even ternary number of the carpels. The discovery 

 by Mr. Hartweg of Begoniads scrambling up trees and shrubs to the height of 25 feet, 

 renders the resemblance almost complete. To Datisca the relationship seems to be well 

 made out. 



The main objection to the association of Begoniads and Cucurbits in the same Alliance 

 arises from the great apparent difference in their placentation ; that of Begoniads being 

 axile, and of Cucurbits parietal. But a careful examination of the ovary of Diplocli- 

 nium Evansianum, acuminatum, incarnatum, &c, shows that distinction to be one of words 

 rather than of essential structure. The ovary of such Begoniads consists of 3 carpels, 

 whose dorsal suture is winged, and whoso margins turn inwards for a considerable 

 distance, each margin forming a plate or placenta, over which the ovules are arranged. 

 This, with the exception of the wing proceeding from the dorsal suture, is the structure 

 of Cucumis, as figured at p. 313, fig. 1, with this difference, however, that the inflexed 

 edges of the earpellary leaves adhere in Diploclinium at a very much more early period than 

 in Cucumis. In Diploclinium acuminatum, when the flower-buds hardly project beyond 

 their fringed bracts, these inflexed edges are easily separable from each other and from 



cexx. 



Fig. CCXX.— Diploclinium Evansianum. 1. a $ flower 

 cross section of the ovary ; 6. a seed ; 7. an embryo 



2. an anther ; 3. a ? flower ; 4. a stigma ; 5. a 



